Try to stack 2 TECs one over the other with thermal paste. Use an old Processor Heatsink for dissipation on the cool side, I have tried this way and cold light a 1W white LED with this and one tealight candle.

Your idea is good, but dangerous!First you should never use 18650 batterys or other LiIons, without a protection circuit.Second: LIIons in series should always have a load balancer circuit.For examle three batteries in series need a 1p 3s balancer.like https://www.ebay.de/itm/3S-11-1V-12-6V-4-6-15A-186...Those circuts you can find for cheap on Amazon AliExpress, Ebay and others.

Those LM2596 does not deliver enough current to get 60EWatts. They can handle a maximum output Power of 15W if equipped with heatsink, without heatsink maximum 10W. So such a module can only light one LED COB module at full power. so if you use 6 COBs each gets less than 2 Watts. I use one LM2596 for each 10W COB. I only have 4x10 COB LEDs

Really good instructable. But I did not use such expensive tools for analysing.I used open logic sniffer program with an Buspirate and 433MHz receiver Module.But I have now built stef mientkis spectrum analyzer and used it that way. http://mientki.ruhosting.nl/data_www/raspberry/doc/si4432_ook_detection.html